1. Field of the Invention
This invention relates to jewelry, and more particularly to a setting structure for securely holding stones therein.
2. Description of Related Art
Jewelry settings are typically used to secure a precious or semi-precious stone, such as a gem or a diamond, to jewelry in a fashionable manner. Jewelry settings are often attached to rings, earrings, or other types of decorative accessories, and are generally made from gold, silver, or other metals and alloys well known in the art.
A jewelry setting typically includes a number of prongs converged at a base and extending outwardly at an angle. The prongs slope upward from the base, with the tips of the prongs defining an area above the base to hold a gem. To improve the retention of the gem in the prongs, it is known to drill a cavity in interior sides of select prongs. The drilled cavities are generally either semi-spherical or cone shaped, depending on the shape of the drill bit used. Alternatively, a C-shaped cavity can be formed on the interior side of the prong by drilling horizontally along the prong's interior side. The prong cavities act as seats and are typically positioned to grasp the tip of the gem. To secure the gem in the setting, the top of the prongs are pushed towards the setting base. This pivots the prongs at their point of contact with the gem, bending the upper portion of the prong downwardly, and thereby clasping down on the gem. As described below, there is a risk of breaking the tip of the stone from the concentrated force of the top of the cavity on the tip during this bending step. Once the prongs are bent towards the gem, the gem is set in place.
The placement of the prongs with respect to the gem generally depends on the location of the gem tips and edges. A gem may have one or more tips at various locations depending on the style of the gem's cut. For example, a marquise cut is an elongated oval shape, with tips at opposite ends of the gem's length. A pear cut is a style of cutting that resembles the outline of a pear, with a tip opposite the gem's bulb. A princess cut is a square cut, with four tips at the four corners of the gem. Typically, gem tips have a cubic or crystalline structure, with faceted sides coming together to form a point. Although a gem's size may change, the lattice angles of the tip will generally stay the same. Thus, for a particular style cut, a gem tip can change it proportion, but its basic shape usually stays the same.
One drawback of the customary jewelry settings described above is that the prong cavity walls typically do not correspond to the shape of a gem tip. The conventional cavities drilled in the prongs have either a rounded or conical cross sectional shape. A gem tip, on the other hand has faceted walls crystalline in shape. Thus, only the corners or the gem tip generally make contact with the cavity walls.
A consequence of ill-matching prong cavities and gem tips is a higher potential for tip breakage. A gem tip is secured in the jewelry setting by bending the prongs inwardly and squeezing the top and bottom walls of the prong cavities together. Prongs with poorly fitting cavities tend to concentrate the bending force at the gem tip's corners, where the gem sides engage the cavity walls. Because only a small area of the gem tip receives the prong bending force, a large amount of pressure is exerted on a small area of the gem tip. This pressure produces stress on the tip and may cause the gem tip to break. A broken gem tip usually requires the gem to be re-cut, decreasing the gem's size and value, and increasing its manufacturing costs.
Additionally, cavities incompatible with the shape of the gem tip can cause the gem to slip free from a jewelry setting more easily. As the prongs and their cavities endure temperature changes and shock from normal use, the gem loosens from the setting over time. With only a small area of the cavity walls in contact with the gem, there is a greater likelihood that the gem will fall out of its jewelry setting.
Another drawback to cavities drilled into the prongs of a jewelry setting can be an increased manufacturing cost in producing the jewelry setting. In order to drill a cavity into a prong, the setting must be fastened in position while a drill bit is used to form the cavity in the prong. Drilling consumes valuable machining time because it is difficult to properly insert the drill bit in the proper position. This increases the cost of creating the jewelry setting. In addition, jewelry settings may become ruined if the drill bit accidentally slips off the prong and drills at an unintended location on the setting.
Therefore, there exists a need for a jewelry setting which contains prong cavities conforming to the shape of gem tips. This will help keep a gem inside the jewelry setting more securely and reduce incidents of tip breakage when prongs are bent inwardly to clamp down on the gem. There also exists a need to produce a jewelry setting more easily and accurately. This will reduce the time, effort, and resultant scrap in the manufacture the jewelry setting.